Accelerated photo-aging of organic coatings used as protective layers for Blu-ray Discs

This article aims to evaluate the impact of UV-light irradiation on the chemical structure and functional properties of organic coatings used to protect the surface and the stored data of Blu-ray Discs. In order to provide a methodology that can make a direct relation between the modification of the chemical structure and the functional properties, a cross-linked aromatic polyester resin with a well-known chemical structure was first studied in photolysis and photooxidation conditions. Characterization of the aging of this material by spectroscopic, calorimetric and thermo-mechanical analyses highlighted chemical and molecular changes linked to the well-known photo-reactivity of the ester functional group (Norrish types I and II reactions, photooxidation, etc.). The photochemical behavior of a real acrylic-based Blu-ray Disc coating was then investigated in the same conditions. Focusing on the influence of photo-aging on the functional properties of the coating, this work showed that on the one hand, the optical and mechanical changes had dramatic effects on the reading of the Blu-ray Disc, but on the other hand, a positive impact of aging was revealed with a significant decrease in the permeability of the coating due to post-cure reactions.